There is an increased interest in HTTP (HyperText Transfer Protocol) streaming of media content, in particular video. Recently, this has evolved beyond simple progressive download to give two new features: adaptivity and live content. The way this is achieved is that the content is partitioned into multiple segments, or files, each corresponding to a small interval of content, for example 10 seconds of content. The client is provided with a manifest file or equivalent file which lists the different segments and where to fetch them and the client fetches them one by one. The split into different segments/files that are fetched via a standard web protocol like HTTP, is also said to be cache-friendly, or CDN (Content Distribution Network) friendly, since it does not require any state in the server or cache, in contrast to streaming servers based on protocols like RTSP (Real Time Streaming Protocol). Multiple levels are possible with intervals and segments. For example, one could do ad insertion, by changing the content during one interval, and then get back to the content stream in the next interval.
Adaptivity is achieved by providing multiple versions e.g. representations of the media content, so that a client can choose to fetch the version which it estimates to be the best given the network performance/download time. From the client's point of view, adaptivity is most easily solved if the segments of the different versions have the same duration, so that the client can simply make a decision for each segment download on which version to choose.
A client node taking part in a HTTP streaming session is faced by two major difficulties. Firstly, in order to enable an optimal streaming session, it is necessary for the client to be able to efficiently and seamlessly switch from one representation to another. This ensures an optimal playback quality of the media session, without unnecessary buffering or downtime, while at the same time ensuring an efficient utilization of available resources. Thus, the client needs to be able to perform representation switching in a reliable and beneficial manner. Secondly, a client is faced with the choice of multiple available representations of a same media segments, and thus needs to be able to, at each moment in time, select the representation that provides the optimal viewing experience. Thus, the client needs to be able to select an optimal representation for its current session.
Based on the above, there is a need for enabling an optimal choice of representations for a client during a streaming session of media as well as a need to enable efficient representation switching for the client.